| Hyperspectral models for estimating SPAD values of kiwifruit leaves |
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| DOI：10.7606/j.issn.1000-7601.2018.06.25 |
| Key Words: kiwifruit hyperspectrum SPAD value red edge parameters estimation models |
| Author Name | Affiliation | | YU Jiao-yang | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, China | | CHANG Qing-rui | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, China | | BAN Song-tao | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, China | | TIAN Ming-lu | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, China | | You Ming-ming | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, China |
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| Abstract: |
| In order to provide a scientific basis for monitoring the conditions of kiwifruit in the northwestern region, the models for estimating chlorophyll content of kiwifruit leaves based on hyperspectrum were constructed. A field experiment were conducted in Jiangjiazhai village of Yangling, Shaanxi Province. During different growth stages, the measurements of the hyperspectral reflectance of kiwifruit leaves were collected using SVC HR-1024i, a portable field spectroradiometer, and also relative chlorophyll content (SPAD) of kiwifruit leaves was measured using SPAD-502, a Chlorophyll Meter. We analyzed the correlations between spectral reflectance, first derivative spectral reflectance, and SPAD values of kiwifruit leaves. Then, single factor regression models and multiple stepwise regression models based on the red edge position, amplitude of the red edge, skewness of the red edge, kurtosis of the red edge were established, respectively, to estimate SPAD values. Our results revealed that: (1) With increase in chlorophyll content, there was a ‘red shift’ phenomenon for the red edge position, in addition, amplitude, area, and kurtosis of the red edge decreased gradually, the shape of red edge skewness curve changed from right to left gradually; (2) The regression models based on srewness of red edge all had good predictive power for SPAD value of kiwifruit leaves; (3) The quadratic polynomial regression models based on red edge of skewness can preferably describe the leaf chlorophyll content, and the regression models based on the red edge of skewness performed best at different growth stages. The determination coefficients for the regression models were 0.821, 0.874, and 0.842, respectively; (4) Compared with polynomial regression models, multiple stepwise regression models were good inversion models for estimating SPAD of kiwifruit leaves, which had better modeling and predictive precision at various growth stages. The determination coefficients of prediction models were 0.848, 0.926, and 0.850, respectively. |
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